"Down-the-hole" drilling tools are often lost, or are retrieved at a great expense, when they jam down the borehole wherein they are operating. This generally occurs due to excavated material lodging or packing around the drilling tools or around drill rods which supply the operating fluid to the drilling tool. Drill rod sections are in threaded engagement with each other and frequently, attempts to extract the drilling tool by pulling on the drill rod simply causes the threads between individual drill rod sections to shear.
It is an object of this invention to provide means for assisting in the extraction of drill rods and drilling tools from boreholes.